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SU‐GG‐T‐278: Clinical Dosimetry of Photon Sources Used in Brachytherapy: Need for ISO Standardization, Based on and Extending the AAPM TG‐43U1 Formalism by Calibration in Terms of Absorbed Dose to Water
Author(s) -
Quast U,
Kaulich T,
Ahnesjö A,
ÁlvarezRomero J,
Donnarieix D,
Hensley F,
Maigne L,
Medich D,
Mourtada F,
Pradhan A,
Zakaria G
Publication year - 2010
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3468671
Subject(s) - dosimetry , brachytherapy , medical physics , quality assurance , monte carlo method , standardization , calibration , photon , nuclear medicine , traceability , detector , absorbed dose , computer science , radiation treatment planning , physics , nuclear engineering , medicine , optics , radiation therapy , engineering , mathematics , statistics , radiology , external quality assessment , quantum mechanics , operating system , software engineering , pathology
Purpose: By calibrating brachytherapy (BT) sources to the TG‐43U1 reference position at 1cm in water, named the nominal absorbed dose‐rate to water , Ḋw ,1 , accuracy and precision for patient treatment will be increased. Traceability must be provided to Ḋw ,1 ‐primary‐standards; which soon become available. Methods and Materials: Efforts have been made in discussions with fellow scientists from many countries, by reviewing concerned literature, and similarities are drawn from documents (e.g. extending TG‐43U1). Results: From the study of primary photon interaction mechanisms, a need was recognized to classify BT‐photon radiation qualities as: high‐energy >100keV, medium energy 40keV to 100keV, and low energy <40keV. It was further recognized that Monte Carlo simulation based primary and scatter dose separation provides characterization for radionuclide BT‐sources and electronic X‐ray BT‐sources, for BT‐detectors and BT‐phantoms. A need was felt for developing reference data‐sets and calibration data of BT‐sources, ‐detectors and ‐phantoms, through which the end‐user medical‐physicist could critically evaluate the data supplied by the manufacturer by using established methods, prior to clinical application. Plastic scintillators appeared to be a choice of detector as future high precision transfer‐standard and high resolution, fast, direct reading dosemeter for detailed quality assurance of BT‐sources, ‐software, ‐planning, and ‐verification. Conclusion: There is the need for international standardization of clinical dosimetry in photon radiation brachytherapy similar to that described in ISO‐21439 (2009) for beta radiation BT‐sources. Based on AAPM TG‐43U1, this planned ISO‐standard will provide guidance for clinical BT‐dosimetry in terms of absorbed dose to water and for estimating the uncertainty of this quantity. Most standardized procedures can be given by referring to AAPM‐ and ESTRO‐reports. Recommendations will be prepared to replace the reference air‐kerma‐rate (air‐kerma strength) by the nominal absorbed dose‐rate to water as basic dosimetric quantity, to increase brachytherapy accuracy and precision and to become consistent with external beam radiotherapy.